This invention relates to a method and apparatus for recovering vapors from a polymer solution. In another aspect the invention relates to a method and apparatus for the recovery of solvent vapors and water vapors from a polymer slurry using steam strippers. In still another aspect this invention relates to a method and apparatus for the reduction of the amount of steam necessarily introduced into the strippers to effect solvent separation.
The production of polymer in crumb form is well known. Existing processes generally utilize steam stripping of a polymer solution to remove and to recover the hydrocarbon solvent. The polymer is coagulated in this process to form a solid crumb which is suspended in water as a slurry. This slurry is subsequently processed in dewatering and drying equipment for final polymer recovery.
A typical process involves polymerizing a monomer system such as for example one comprising one or more conjugated dienes in a solution medium and the recovery of the polymer from the solution in which they are produced. Recovery is generally accomplished by steam stripping the polymer solution. In a typical steam stripping process, a polymer solution comprising polymer and liquid solvent, and water are introduced into a primary stripper operating slightly above atmospheric pressure. By using steam as a stripping medium, a substantial portion of the solvent is removed from the polymer solution in the primary stripper. The water and solvent vapors from the primary stripper are passed to suitable purification and recovery means. The bottom product, now in slurry form and now relatively lean in solvent, is passed to a secondary stripper where steam is again introduced to effect solvent separation. In existing processes some of the vapors are recovered from the secondary stripper and are introduced into the vapor zone of the primary stripper. Although a substantial portion of the vapors are recovered from the secondary stripper, the bottoms product from the secondary stripper still contains some solvent which is ultimately removed from the system and lost during final processing of the polymer.
An object of this invention is a method and apparatus for reducing the cost of operating a polymerization process. Another object of this invention is a method and apparatus for recovering polymerization solvent.